diff --git a/output/src/view.rs b/output/src/view.rs
index fc6411a..1857ce2 100644
--- a/output/src/view.rs
+++ b/output/src/view.rs
@@ -9,12 +9,14 @@ pub trait View<O, U> {
         Err(format!("View::view_word: no words defined: {word:?}").into())
     }
     fn view <'a> (&'a self, output: &mut O, dsl: &'a impl Language) -> Usually<U> {
-        if let Ok(Some(expr)) = dsl.expr() {
-            self.view_expr(output, &expr)
-        } else if let Ok(Some(word)) = dsl.word() {
-            self.view_word(output, &word)
-        } else {
-            Err(format!("{dsl:?}: invalid").into())
+        let is_expr = dsl.expr();
+        let is_word = dsl.word();
+        match (dsl.expr(), dsl.word()) {
+            (Ok(Some(e)), _          ) => self.view_expr(output, &e),
+            (_,           Ok(Some(w))) => self.view_word(output, &w),
+            (Err(e),      _          ) => Err(format!("invalid view expr:\n{dsl:?}\n{e}").into()),
+            (_,           Err(w)     ) => Err(format!("invalid view word:\n{dsl:?}\n{w}").into()),
+            (Ok(None),    Ok(None)   ) => Err(format!("empty view:\n{dsl:?}").into()),
         }
     }
 }